Add screenshot code to olive scriptless demo

orx-olive/src/demo/kotlin/DemoOliveScriptless01.kt

@@ -1,6 +1,8 @@
+import org.openrndr.Extension
 import org.openrndr.Program
 import org.openrndr.application
 import org.openrndr.color.ColorRGBa
+import org.openrndr.extensions.SingleScreenshot
 import org.openrndr.extra.olive.Olive
 import org.openrndr.math.IntVector2
 
@@ -13,6 +15,21 @@ fun main() {
         }
         program {
             extend(Olive<Program>()) {
+                // -- this block is for automation purposes only
+                if (System.getProperty("takeScreenshot") == "true") {
+                    scriptLoaded.listen {
+                        // -- this is a bit of hack, we need to push the screenshot extension in front of the olive one
+                        fun <T : Extension> Program.extendHead(extension: T, configure: T.() -> Unit): T {
+                            extensions.add(0, extension)
+                            extension.configure()
+                            extension.setup(this)
+                            return extension
+                        }
+                        extendHead(SingleScreenshot()) {
+                            this.outputFile = System.getProperty("screenshotPath")
+                        }
+                    }
+                }
                 script = "orx-olive/src/demo/kotlin/DemoOliveScriptless01.kt"
                 program {
                     extend {